TCS230 output problem. HELP URGENT!!!

Discussion in 'The Projects Forum' started by thavamaran, May 22, 2009.

  1. thavamaran

    Thread Starter Active Member

    Feb 21, 2008
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    Hi guys, im working on TCS230, a CMOS color sensor, so im really confused what the problem will be. please someone.


    actually my sensor was working well, but the output, when i measured it in oscilloscope, its not stable, like an example.

    i triggered to blue filter and measured a blue printed A4 paper, so during my measurement in oscilloscope, it varies greatly, it alternates crazily, like 3,98khz to 4.59khz and then back to 3.8khz, and go back to 4.83 khz, and return back to 3.39 khz, it just keeps alternating. so what i did was, i concluded that external light source is giving too much of trouble and i get a black box, stick it on my PCB all around the white LED and also the sensor, its covering around, the sensor is covered by 1.7cm plastic around it. So when now i measure it, the waveform actually got worst, it varies like hell and there is noise in the waveform now. its getting crazy. i really got no idea what to do.

    my circuitry is like very simple, a color sensor and two white bright led by the side of it, i just design it by myself, do anyone can give me idea what would be the problem, please someone, and is there certain specification how the LED must be fixed by the side of sensor? please someone help me. cause once the sensor is stable only, i could do my pixel level analysis and sensitivity analysis.
     
  2. Wendy

    Moderator

    Mar 24, 2008
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    Verbal doesn't really tell much, pictures are always better. Schematics are best.
     
  3. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Did you use a decoupling capacitor (ca. 0.1 μF) on the powerlines?
    How is the oe\ line driven?

    [​IMG]

    How is the frequency scaling set?

    Greetings,
    Bertus
     
    Last edited: May 22, 2009
  4. thavamaran

    Thread Starter Active Member

    Feb 21, 2008
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    0
    Sorry guys, i was not able to think about uploading sch all, got jammed, here is the schematic.
    bertus, i connect a cap on the breadboard when i test, and how to produce a low impedance electrical connection? and the frequency scaling is set to 100%.
     
  5. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    A direct connection between oe\ and ground is good enough.
    The capacitor should be as close as possible to the power pins.
    Are the selector pins connected or open?
    If they are open they can give problems.
    Connect unused pins either to +Vdd or ground.
    So in your case connect S0 and S1 to +Vdd.

    Greetings,
    Bertus
     
  6. thavamaran

    Thread Starter Active Member

    Feb 21, 2008
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    Hi bertus, all the pins are connected, S0 and S1 are connected to Vdd. always connected. So you suggest the problem might be the capacitor not connected close? cause im also having noise and spikes in the waveform.
     
  7. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Yes. If the capacitor is to far away, the leads may carry the pulses.

    Greetings,
    Bertus
     
  8. thavamaran

    Thread Starter Active Member

    Feb 21, 2008
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    Ok bertus, so you think the problem might be with the supplied. i will redo my board then. thanks a lot. is there anything else you feel i should do?

    Thank you
     
  9. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    What do you use for a powersupply?
    Is it a LM317 like or a 7805 like?
    Both types need a capacitor of 0.1 μF to 0.33 μF near the regutalor.
    This capacitor is used to suppress oscillation of the regulator.

    Greetings,
    Bertus
     
  10. thavamaran

    Thread Starter Active Member

    Feb 21, 2008
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    Hi bertus, im using lm317. i need another favor, i dont really get about the bits. how can i actually find out what color sensor bits?
     
  11. thavamaran

    Thread Starter Active Member

    Feb 21, 2008
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    0
    Hi guys, actually im having a problem with my sensor characteristic, its like this, when it reads for an example red, its gives a frequency, when its blue it gives a frequency, but when its capturing both colors, like say in an image there will be a lot colors, so when it captures a pixel with two colors, it averages them, so how can i overcome this problem? what can i do?
     
  12. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    It more looks like an optical problem.
    The area the sensor looks at is to large.
    Is there a possebility to use a lens to focus the area?

    Greeitngs,
    Bertus
     
  13. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    You do not understand the function of the sensor. To quote from the datasheet - it is a light intensity to frequency converter. Notice that color is not mentioned. The ouput frequency is solely dependent on the intensity of the incident light.

    If you with to use these sensors for colorimetry, then you will need three of them, plus the optical filters for the three colors. One can output for blue intensity, one for red, and the other for green. That is the only way these devices can show color.

    Here is the Wikipedia article - http://en.wikipedia.org/wiki/Colorimetry
     
    Last edited: May 28, 2009
  14. pashasv

    New Member

    Jun 3, 2013
    1
    0
    Dear colleagues!
    Experience shows that this device is influenced by other devices are in this diagram. To eliminate the instability of frequency signals to the stage of testing and debugging the wiring is to eliminate all unnecessary at this time of the device.

    Sorry for my bad English.
     
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